A mobile terminal such as a smartphone, a tablet terminal and a personal computer is mounted with a digitizer system for detecting positional information on a liquid crystal display as digital information which is inputted by a coordinate indicator such as a touch pen. In this system, the positional information is detected by means of magnetic coupling between the coordinate indicator and the detector using an A.C. magnetic field of about 100 kHz to about 1 MHz. For the purpose of enhancing read sensitivity or positional accuracy in the digitizer system, a shielding plate is disposed on a backside surface of the detector to thereby suppress adverse influence of unnecessary magnetic field from outside.
In order to enhance the read sensitivity or positional accuracy in the digitizer system and meet requirements of the market, such as reduction in weight and thickness of the device, there are disclosed the technology in which a ferrite plate or a sheet-like parts formed by dispersing ferrite particles in a rubber or plastic material is used as a shielding plate (Patent Literature 1), the technology using a magnetic thin plate formed of permalloy or amorphous metal (Patent Literature 2), and the technology using ferrite, a ferrite-containing body, an iron carbonyl compacted body, a permalloy compacted body and a sendust compacted body (Patent Literature 3).